Method of analyzing a web of paper



March 22, 1955 H, DAVls METHOD OF ANALYZING A WEB OF PAPER OriginalFiled Feb. 23, 1949 United States Patent METHOD OF ANALYZING A WEB OFPAPER Harold M. Davis, North Calais, Vt., assignor to Precision Paper,Inc., Calais, Vt., a corporation of Vermont Original applicationFebruary23, 1949, Serial No. 77,763, now Patent No. 2,608,912, datedSeptember 2, 1952. Divided and this application August 27, 1952, SerialNo. 306,643

2 Claims. (Cl. 73-159) The present invention relates to the manufactureof paper wherein a stream of an aqueous wood pulp suspension is flowedout of a head box upon a moving screen or wire to form thereon a web ofpulp. The web of pulp is subsequently processed, as by drying andcalendering, to produce a web of paper. This application is a divisionof my application, Serial No. 77,763, filed February 23, 1949, nowPatent No. 2,608,912, dated September 2, 1952.

During my extensive research, I have used the following method ofselecting samples of the web of paper to determine the action of thepaper making machine. In working with a F ourdrinier machine producing aweb 132 inches wide, I divided the web into 22 tracks each six inches inwidth and determined the changes in basis weight which took place ineach track. 'For example, assuming the machine was running at a speed of550 feet per minute, a piece of paper 72 feet long in the longitudinaldirection of the web represented the action of the paper machine duringa period of eight seconds of machine running time. By cutting this piecetransversely of the web to form six pieces each 12 feet long, I obtainedsix pieces each representing 1% seconds of machine running time. Bycutting each of these pieces in the longitudinal direction of the web toform 22 pieces each 6 inches wide, I obtained six samples eachrepresenting the action taking place in 1 /3 seconds of machine runningtime in each of the 22 tracks into which I divided the web. The basisweight of each sample was determined by weighing.

Employing this method of sampling I found that permanent heavy and lightstreaks lengthwise of the web of paper were present for mile after mileand caused a variation in basis weight across the web up to threepounds. In this specification, I refer to the heavy streaks as hills andto the light streaks as valleys." I also found that there is areoccurring cycle of basis weight variations in all longitudinal linesof the web, each cycle corresponding to about 5 seconds of machinerunning time. I also found a third type of basis weight variation, whichis a flash but random variation, in which from two to nine trackscombine for about one second to change basis weight in the samedirection but not necessarily by the same amount in each track. Both ofthese flash variations are equally evident in 8-second tests of 72 fleetof paper and in many hours of tests sampled once an our.

These three types of basis weight variation have led those skilled inthe art to erroneous interpretations of the action of paper makingmachines. It has been common practice to make certain adjustments in thepaper making machine, such as adjustment of the slice in the Fourdriniermachine, as dictated by the visual appearance of the flow on the wireand based upon samples selected periodically from the finished paper.The most common sampling practice has been to tear four separatelaterally spaced pieces from the end of a reel and trim each to measure24 by 36 inches.

No set of samples obtained by this common method of sampling furnishedaccurate information as to the true character of the web of paper beingproduced. Thus, the portion of the width of the web represented by eachsample might contain a high hill or a deep valley or both but no sampleindicated this because it gave only the average basis weight of thisportion of the web, e. g. the average of the hills and valleys.Furthermore, no

set of samples represented the average basis weight of any longitudinalportion of the web formed during'any one completed cycle of almostinstantaneous changes in basis weight which reoccur and are completedabout every 5 seconds.

Based upon this information, the character of the stream of aqueous pulpsuspension was controlled by adjustment of the paper making machine tocontrol the character of the web produced. It is obvious that at timesand places adjustments were made when they should not have been made andat other times and places no adjustment was made when one should havebeen made. In view of this and in the light of my discoveries previouslymentioned, it is obvious why paper manufacturers concluded that theprofile of the web continually changes and never follows a substantiallyfixed pattern. It is equally obvious that paper produced under suchconditions would vary greatly in basis weight.

The present invention provides a method for sampling the web of paperwhereby the true character of the profile of the web may be accuratelydetermined. In the practice of the invention, the web is considered ascomposed of a plurality of narrow longitudinally adjoining tracks. Aplurality of pieces of paper are selected from each track to obtain anaverage of each of the cycles of about five seconds duration. Thus, theaverage basis weight of the pieces selected from each track isrepresentative of the basis weight of the paper in each trac In thepractice of the invention I have found it convenient and practical tosever a plurality of the outer convolutions of a reel of papertransversely along two spaced parallel lines extending across the entirewidth of the web and thereby obtain a set of a plurality of superimposedpieces of paper. The average basis weight of these pieces of paper isrepresentative of the basis weight of the web. Then, a measure may beobtained of the relative basis weight of each of narrow adjoiningportions of this set of pieces of paper in the transverse direction ofthe web. One way of obtaining this measure is by severing the set ofpieces of paper along spaced lines in the longitudinal direction of theweb to obtain a group of a plurality of samples of paper from each of aplurality of narrow adjoining longitudinal portions of the 'web and thenweighing each of the groups.

The invention is illustrated further by the following description inconjunction with the accompanying drawing: in which,

Fig. 1 is an end elevational view of a reel of paper;

Fig. 2 is a perspective view, partly broken away, of a set of aplurality of superimposed strips of paper formed by severing a pluralityof the outer convolutions of a reel of paper along spaced parallel linesextending across the width of the reel;

Fig. 3 is a perspective view of one of a plurality of multiple samplesof paper formed by cutting the set illustratled in Fig. 2 along the dotand dash lines of Fig. 2; an

Fig. 4 is a front elevational view of a weighing instrument having amultiple sample of paper positioned thereon for weighing.

In the practice of the present invention, the paper making machine islooked upon as producing a plurality of narrow longitudinal strips ortracks which nevertheless are integral and taken together make up theentire width of the web. Consequently, it is necessary to obtain ameasure of the relative basis weight of each of such strips or tracks.In order to obtain a true indication of the exact nature of the profileof the web being produced, the interpretation should be based upon theaverage of a number of samples in each track. In practice I takeadvantage of the fact that the samples from the four or five outerconvolutions of an ordinary reel cover all phases of the five secondreoccurring cycles of variations in basis weight. The number ofconvolutions to be sampled and the length of each sample may be suitedto fit the conditions in any mill. I prefer to take a sample from eachof the eight outer turns of the reel but a smaller or greater number maybe employed, the essential being to obtain an average which isrepresentative of the average of each of the reoccurring cycles of to 8seconds duration.

One method of practicing the invention is illustrated in theaccompanying drawing. Thus, the eight outer convolutions of a reel ofpaper 10 are cut along parallel lines, as indicated by the dotted linesin Fig. 1, spaced 18 inches apart and extending across the entire Widthof the reel. This produces a set 11 of eight superimposed pieces ofpaper as indicated in Fig. 2. A measure of the relative basis weight ofeach adjoining longitudinal track of the web may be obtained by cuttingthe set 11 along parallel lines spaced 6 inches apart and extending inthe longitudinal direction of the web as indicated by the dot and dashlines in Fig. 2. This produces a plurality of multiple samples 12 eachcontaining eight superimposed sheets 6 by 18 inches which equals thearea of the common 24 by 36 inch (24/36 500) sample and may be weighedon the customary ream scales 13 as illustrated in Fig. 4. The eightsheets in each sample 12 averages the flash variations in basis weightin the longitudinal track of the web from which it was taken.Consequently, by comparing the weights of the samples 12, a measure ofthe relative basis weight of the paper in each track is obtained. If theedges of the reel have been trimmed, the edge samples will be slightlyless than 6 inches wide and their weights may be adjusted byinterpolation.

In this method of sampling, the size of the samples may be changed toadapt them to be weighed upon any customary ream scales. Thus, insteadof samples 18 inches long, longer or shorter samples may be used so thatthe combined area of the eight sheets in each multiple sample is suchthat it may be Weighed on any available ream scales.

I claim:

1. In the manufacture of a web of paper wherein a stream of an aqueouspulp suspension is deposited upon a moving screen, the method fordetermining the character of the web being produced which comprisessevering a plurality of the outer convolutions of a reel of papertransversely of the reel along two spaced parallel lines extendingacross the entire width of the web to obtain a set of a plurality ofsuperimposed pieces of paper equal to the number of said convolutionssevered, severing said set of pieces of paper along spaced lines in thelongitudinal direction of the web to obtain a group of a plurality ofsamples of paper from each of a plurality of narrow adjoininglongitudinal portions of the web of equal width, the combined Width ofsaid portions being substantially equal to the width of the web, andweighing each of said groups thereby separately determining the averagebasis weight of each of said portions.

2. In the manufacture of a web of paper wherein a stream of an aqueouspulp suspension is deposited upon a moving screen, the method fordetermining the character of the web being produced which comprisessevering a plurality of the outer convolutions of a reel of papertransversely of the reel along two spaced parallel lines extendingacross the entire width of the web to obtain a set of a plurality ofsuperimposed pieces of paper equal to the number of said convolutionssevered, and measuring the relative average basis weight of narrowadjoining portions of said set in the transverse direction of the web.

References Cited in the file of this patent UNITED STATES PATENTS1,429,899 Mallory Sept. 19, 1922 2,374,847 Vollrath May 1, 19452,426,312 Lewis et a1 Aug. 26, 1947 2,466,615 Rusca et al. Apr. 5, 1949OTHER REFERENCES Tappi Standards, 1948 T400m41 (1 sheet), T411m44 (2sheets), T426m46 (2 sheets).

